How does urine pH affect the plasma half-life of pseudoephedrine in Benadryl Allergy Relief Plus Decongestant Capsules?

For pseudoephedrine in Benadryl Allergy Relief Plus Decongestant Capsules, urine acidification markedly decreases plasma half-life and alkalinisation increases it; the plasma half-life is approximately 5.5 hours when urine pH is maintained between 5.0 and 7.0.